A plastic injection molding machine operates 348 days a year. It is the bottleneck workstation in a process that produces plastic housed wall clocks.

Industrial engineers collected data on the probability of machine breakdowns, the costs of preventive maintenance, and the cost of a breakdown.

The cost of preventive maintenance is high due to performing it between 1 and 4 a.m. each day by two machine experts. The preventive maintenance cost is $1,980 per day including replacement parts, cleaning, and software upgrades. The cost of a breakdown of $1,850 is also high because the downstream workstations can only work until all work-in-progress inventory is completed; then the entire process must stop.

Number of molding machine breakdowns per day Probability of a breakdown 0 1 2 3 4 0.32 0.28 0.22 0.13 0.05